1. Field of Invention
The present disclosure relates to a through tubing submersible pump having a mechanically locking seal for sealing flow between the pump and the tubing.
2. Description of Prior Art
Submersible pumping systems are often used in hydrocarbon producing wells for pumping fluids from within the well bore to the surface. These fluids are generally liquids and include produced liquid hydrocarbon as well as water. One type of system used in this application employs an electrical submersible pump (ESP). ESPs are typically disposed at the end of a length of production tubing and have an electrically powered motor. Often, electrical power may be supplied to the pump motor via cable strapped to the exterior of the production tubing. ESP's may comprise centrifugal pumps or progressing cavity pumps. Progressing cavity pumps (PCP) are positive displacement pumps that consist of a helical steel rotor inside a synthetic elastomer bonded to a steel tube (stator). As the rotor turns within the stator, fluid moves through the pump from cavity to cavity. The resulting pumping action increases the pressure of the fluid, allowing production to the surface.
FIG. 1a depicts a partial sectional view of a prior art submersible ESP system disposed in a wellbore. The ESP production system 2 shown comprises a pumping system 12 on production tubing 8; where the tubing 8 is suspended within a cased wellbore 4. The downhole pumping system 12 comprises a pump section 13, a seal section 14, and a motor 17. The seal section 14 equalizes fluid pressure in the motor 17 with pressure in the wellbore fluid. An electrical conduit 15 is strapped externally to the tubing 8, pump section 13, and seal section 14. Energizing the motor 17 drives a shaft (not shown) coupled between the motor 17 and the pump section 13.
Inlets 16 provided at the bottom of the pump section housing provide a passage for formation fluid to flow from the annulus between the casing 5 and system 12 into the pump section 13. Perforations 7 project into an adjacent formation 6 to provide a source for the formation fluid. As illustrated by the arrows, the formation fluid flows from the formation 6, through the perforations 7, up the annulus, and to the inlets 16. Fluid drawn into the inlets 16 is pressurized within the pump section 13, and then discharged into the tubing 8.
When installing an ESP through tubing, the pump assembly is lowered into and suspended within the production tubing. Typically the motor is mounted to the lower end of the production tubing, and the pump assembly stabs into engagement with the drive shaft of the motor. In this configuration the pump discharges into the production tubing. FIG. 1b provides in partial sectional view an example of a prior art through tubing conveyed ESP initially deployed in a wellbore and before installing the pump. In FIG. 1b, a tubing deployed drive system 19 is shown on production tubing 8 disposed in a cased wellbore 4. The tubing deployed drive system 19 illustrated comprises an engaging receptacle 20, a seal section 14, and a motor 17.
FIG. 1c depicts a partial sectional view of an example of a through tubing conveyed ESP system having a pump installed. In FIG. 1c, an ESP production system 2 is formed when a downhole pumping assembly 21 is inserted within a tubing deployed drive system 19, a packer 22 is installed within the tubing 8 at the top of the pump, and a tubing anchor 23 is installed within the tubing 8 at the top of the packer. The downhole pumping assembly 21 comprises an engaging base (not detailed) compatible with the engaging receptacle 20, an inlet section (not detailed), a pump section, and a receptacle (not detailed) suitable for use with downhole tooling commonly found in oilfield practice. A stinger on the packer 22 sealingly inserts into the tooling receptacle at the top of the pump assembly 21, and a stinger on the tubing anchor 23 sealingly inserts into a like receptacle at the top of the packer. The packer 22 serves to isolate the produced fluids from the well bore, and the tubing anchor 23 serves to secure the pumping assembly 21 within the tubing 8.
Energizing the motor 17 then drives shafts (not shown) variously coupled between the motor and the pump assembly 21. Inlets 16 are provided on the engaging receptacle 20 wherein formation fluid can be drawn into the inlets 16 then into the inlet section of the pump assembly 21 and up into the pump section. Formation fluid flow, represented by arrows, flows into the annulus from perforations 7 extending a surrounding hydrocarbon producing formation 6. The pump discharges the formation fluid through the packer 22 and the tubing anchor 23 into the tubing 8. Packer 22 provides sealing between the pump discharge and the inlets 16, thereby maintaining sufficient pressure in the tubing 8 to force the production fluid up the well bore 4 to the wellhead 9. Upon reaching the wellhead 9, the production fluid can be distributed via an attached production line 10.